Hydraulic pump



July 13, 194s. c, H, RYSTRQM l 2,445,281

HYD-RAULIC PUIIP Fiied oct. 4, 1945 Patented July 13, 1948 y HYDRAULIC PUMP Charles H. Rystronnltockford, Ill. Application October 4, 1.945, Serial No. 620,346 s claims. (ci. 1oz-162) My invention relates vgenerally to hydraulic,v

pumps,Y and more particularly to hydraulic pumps of the swash plate type, which may also be used as hydraulic motors..

In pumps of the swash plate type, the pistons or plungers are carried by a rotating barrel x which is pressed against a head, and, as the barrel rotates, the pistons at one side of the barrel are discharging the hydraulic fluid under pressure, while the pistons on the other side of the barrel are executing a suction stroke. The forcesA acting on the barrel, tending to move it away from the valve seat surface, are therefore greater on one side than on the other, which tends to cause thev cylinder barrel to tilt. Such tilting tendency of the barrel places strains on the bar`4 provide a pump or motor of the swash plate type, i

in which the forcesacting upon the pump barrel are substantially balanced,. so that the cylinder barrel presses uniformly against the valve sur- '1 face formed on the head of the pump.

A further object is to provide an improved l' pump or motor of the swash plate type having a plurality of concentric rows of pistons and cylihders, with an improved head construction whereby the pistons of the two rows may be'operated in opposite phase., that is, while the outer row of pistons on one side of a diametral line are executing a discharge stroke, the adjacent pistons are executing a suction stroke, and vice versa, so that at all times the forces tending'to press the cylinder barrel against the head will be substantially balanced. V

plate f A further object is to provide an improved head construction including outlet and'inlet passageways, whereby a plurality of concentric rows of pistons and cylinders may be employed' in"a` pump or motor of the swash plate type.

Other objects will appear' from the following description, reference being had to the accompanying drawings, in which:

Fig. 1 is a central longitudinal sectional view of the improved pump and motor; and

Fig. 2 is a sectional view thereof, taken on the line 2--2 of Fig. 1.

Referring to Fig. 1, the pump or motor comprises a body casing III having ,heads I2 and I3 .l

secured thereto as by tie bolts (not shown).` A shaft I4 is mounted for rotation in an'anti-friction thrust bearing I8, secured in the head plate I2, 'and in an anti-friction bearing I3. suitably I vmounted in the head I3.

An 011 ,seal zaligheid in place by a gland 22 secured to the head I2." A cylinder barrel 24 is keyed to the shaft I4 and 4is pressed against the'head I3 by a spring 23 compressed between a washer 28 and the barrel The contacting valve surfaces of the head I 3 and barrel 24 are suitably finished so as .to pro-f vide an oil tight seal. The barrel is provided with a suitable number of outer cylinders 30 and `a similar row of inner cylinders 32. Pistons or 'plungers 34 are reciprocable in the outer cylinders, while plungers 3B are reciprocable in the inner row of cylinders.

Each of the plungers 34 and 36 is provided with a head 38which 'is recessed to receive a hardened steel .ball 40 vand isvretracted from its cylinder by a coil spring 42 compressedbetween the barrel 24 and the head 38. The balls 40.0f the outer row of ,plungers 33 have at surfaces slidably engaging a thrust ring 44 mounted in an anti-friction bearing 46, having thrust rollers 41 and radial rollers 43. The anti-friction bearing 46 is mounted on an annular block 50 which is suitably secured to the head I2. lIt will Vbe noted that the surface of the block l5l! upon which the anti-friction bearing 46 rests is at an angle with respect to theraxis of the shaft I4. I

In a similar manner, the'plunger's 36-of vthe -inner row are in engagement with a thrustfplate 52 mounted on an yanti-friction bearing 54 carried. by an `annular mounting blockV 53. .The blocks and 56 are suitably secured to-thefhead I2 .as by cap screws extending ythrough thevhead I2 and into theblocks or in any lothersuitable manner. It will be noted that the surface ofthe block 56 upon which the` anti.frictiofrv` rests is inclined'with reference to the fa iso shaft I4 in a direction opposite to that n the corresponding surface of the blockli si,- clined.l The block 56 is provided with a firing bushing. for the shaft I4. t 1 y The head I3/has an outlet passageway 76011 and an inlet passageway 62 formed therein. '.Asmbest shown in Fig. 2,'the passageway 62fhas ari-arcuate portion 62a inv alignment vwith the outer, row of cylinders 30 and a portion vk62h in alignment 'with the inner row of" cylinders 32, the-'portions 62a and B2b Ybeing joined by a portion 62e. In a similar manner, the passageway has an outer portion Gila'which is in alignment with-the outer cylinders 30. and 'a'portion- 60h in align'- ment with the inner row of cylinders 32, the por'- tions 6ta-and 60h being Joined by aconnecting portion ttc. y y

:Adi

b an v 4 I'he cylinders 30 have ports 3l which, as the barrel 24 rotates, are in alignment with a substantially semi-circular port 63 during substantially one-half a revolution, and with a substantially semi-circular arcuate port 33 during the remainder oi' the revolution. It will be noted that the port Il is in communication with the passageway l2 while the port 69 is in communication with passageway Il. In a similar manner, ports 1li of the cylinders 32 of the inner row are in registry with ports 'l2 and ports 13 each during substantially one-half a revolution. The port 12 communicates with the portion Bllb of the passageway (Il, while the port 13 communicates with the portion 2b of the passageway 62.

Assuming that the shaft I4 is driven in the direction of the arrow marked thereon in Fig. 1,

' that is, counterclockwise as viewed in Fig. 2, it

will be seen that the plunger 36 which is directly above the shaft I4 is commencing movement into its cylinder 32, discharging the oil therefrom through the port 12 and passageway 60 from which the lubricant may flow through an outlet conduit 14 which is suitably connected to a cover plate 'II attached by cap screws 13 to the head I3. On the other hand, the piston 36 positioned directly beneath the shaft I4 is commencing retractile movement under the influence of its com pressed spring 42, and therefore drawing oil from the portion 32h of passageway 62. Oil is supplied to the passageway 62 through a conduit 30 which is suitably connected to a cover plate 32 secured to the head I 3 by cap screws 34. f

n the other hand, the outer piston 34 above the shaft I4 is commencing its suction stroke, while the piston 34 directly below the shaft I4 is commencing its discharge stroke. The remaining plungers are in intermediate positions. Thus the forces applied to the cylinder barrel 24 by all of the plungers or pistons 34, 36, tend to balance so that there is but a relatively small net force tending to cause the cylinder barrel to tilt in a manner such that it does not contact the head i3 throughout the contacting surface thereof.

It is clear that the forces acting upon the cylinder barrel 24, due to the compressive strokes of the outer row of plungers 34, have a greater torque effect tending to tilt the cylinder barrel 24 than do the forces due to the compressive strokes of the inner row of plungers 36. and thus a complete torque balance is not effected by the construction shown, in which the plungers 34 and 33 are of the same diameter, and of the same number. However, for practical manufacturing and servicing reasons, it is desirable to have the plungers 34and 38 interchangeable, and the cylinders and 32 of the same diameter. If des ired, the number of plungers 34, or the eil'ective areas thereof. may be reduced by about one-third in order to cause the torques applied to the cylinder barrel due to the compressive strokes of the plungers 34, to balancethe torques due to the compressive strokes of the plungers 36. Such re- `ductionof one-third in the number or effective areas of plungers 34 would accomplish `such torquebalance if the plungers 34 are 1.5 times as'far from the axis of the shaft I4 as the plungers I., Such complete balancing of the torques, either byv decreasing the number of plungers in the outer row, or by decreasing the diameters thereof, is contemplated in pumps or motors in which longservice-free life and precision operation are important requirements. However, for ordinary use, the pump may be constructed with equal numbers of plungers 34 and 34. and with apparatus through the conduit 80, rotation of the cylinder barrel 24 and shaft I4 may be effected, Vprovided free discharge of the hydraulic fluid from the conduit 14 is permitted. When used either as a pump or as a motor, the load Aor torque on the shaft I4 is more uniform due to the substantial equalization of the forces applied to or.

by the plungers. This is of particular advantage when the apparatus is used as a motor to drive a machine or part at constant uniform speed. Due to the use of a plurality of concentric rows of pistons and cylinders, the apparatus of small overall dimensions will have large displacement when used as a pump, and conversely, when used as a motor, is capable of delivering greater power than conventional types of fluid motors of equal overall dimensions. Thus in the claims, wherein the invention is generally defined as a pump, it will be understood that a similar structure used as a motor is intended to be included.

While I have shown and described a preferred embodiment of my invention, itvwi11 be apparent that numerous variations and modifications thereof may be made without departing from the underlying principles of the invention. I therefore desire, by the following claims, to include within the scope of the invention all such variations and modifications by which substantially the results of my invention may be obtained through the use of substantially the same or equivalent means.

I claim:

1. In a pump of the swash plate type, the combination of a housing, a head at one end of the housing, said head having four arcuate ports each extending throughout substantially a semicircle and at two different radial distances from the center of the head, said head being provided with two passageways each in communication with an inner port and a diametrically opposite outer port, a cylinder barrel having a pair of concentric rows of cylinders having ports respectively registrable with the inner and outer arcuate ports, a plunger in each of the cylinders, means to cause rotation of said cylinder barrel, and two swash plates engaged by the plungers to cause reciprocation of each of said plungers once during each revolution of the cylinder barrel, the swash plates being oppositely inclined with respect to the axis of the barrel thereby to cause the reciprocation of the plungers of the inner and outer rows to take place in opposite phase.

2. A pump of the swash plate type having a rotatable cylinder barrel having two concentric rows of cylinders therein, a spring retracted plunger in each of said cylinders, means to rotate the cylinder barrel, and a stationary swash plate engaging the ends of the plungers in each row, the swash plates being inclined in opposite directions with respect to the axis of the cylinder barrel. (n

3. In a pump of the swash plate type, a housing, a cylinder barrel rotatable within said housing and bearing against one end thereof, a shaft for rotating said barrel, said barrel having a piurality of concentric rows of cylinders formed therein, the end of the housing against which the ing against which the barrel bears being provided l0 with two passageways, one connecting all the ports which are in registry with cylinders in which the plungers are executing discharge strokes, and the other passageway connecting all ports which are in registry with cylinders in 15 which the plungers are executing suction strokes. CHARLES H. RYSTROM.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 1,714,1'48 Weldy May 21, 1929 y 2,337,821 Huber Dec. 28, 1943 FOREIGN PATENTS Number Country Date v 527,997 Germany June 3, 1930 

